PG&E usage data does not balance with Tesla App data?

[SolarBob]

Ran a spread sheet for 2021 from Jan 1st until Oct 31st using PG&E data on their web site.

Long spread sheet hour by hour, day by day, the net total result is -354.87 kWh for the year.

The Tesla app shows for the year:

Home Usage = 12,336 kWh
Solar Energy = 13,108 kWh

= -772 kWh

Why are they so different?

Comments?

 

[arnolddeleon]

3.4% difference

Really need more information. What kind of Solar setup do you have? Different Tesla/Solar City installations have different methods of reporting production and usage with different precision and accuracy. Do you have Powerwalls? They have overhead which depending on where you measure could make a difference.

 

[SolarBob]

16.32 kW Solar Panel System
Estimated energy produced: 15,789 kWh /yr
2 Powerwalls

48 panels, Thanks for responding.

 

[getakey]

3.4% difference

Really need more information. What kind of Solar setup do you have? Different Tesla/Solar City installations have different methods of reporting production and usage with different precision and accuracy. Do you have Powerwalls? They have overhead which depending on where you measure could make a difference.

3.4%? Looks more like 100% difference

 

[holeydonut]

3.4%? Looks more like 100% difference

I guess we should price out the ~417 kWh and say it's a $100 error

I honestly don't know how you all triangulate the Tesla App with PG&E. (edit: for me,) the Tesla App is always off compared to what PG&E meters. And there seems to be no way to really get to the bottom of it without literally slapping in another meter somewhere as a control.

For example, Tesla says I've been a net exporter to the grid to the tune or 900 kWh since the system went live in early 2021.

But PG&E's black and white bills and CCA NEM bills say I've been a net exporter of 1,657 kWh since they started hitting me with bills under NEM2-MT (PS).

Since the error is in my favor, I guess I just kind of shrug it off. But I can only imagine how annoying it is if the error goes the other way. I'm curious if there is a way to determine what is "right".

 

[yblaser]

Ran a spread sheet for 2021 from Jan 1st until Oct 31st using PG&E data on their web site.

Long spread sheet hour by hour, day by day, the net total result is -354.87 kWh for the year.

The Tesla app shows for the year:

Home Usage = 12,336 kWh
Solar Energy = 13,108 kWh

= -772 kWh

Why are they so different?

Comments?

Maybe I'm missing something, but why would you not compare it to what the app reports as the grid usage. Using just home and solar misses the contribution/loss from the powerwalls.

3.4%? Looks more like 100% difference

If PG&E reported exactly zero net usage would that be an infinite difference then?

 

[aesculus]

Since the error is in my favor, I guess I just kind of shrug it off. But I can only imagine how annoying it is if the error goes the other way. I'm curious if there is a way to determine what is "right".

Unless the PG&E meter is broken, they are right. They are revenue grade since they are charging you (or paying you) for the energy. Tesla is just using CTs which are not as accurate.

I have not done the billing comparison yet but just doing some checking via the meter occasionally its with a few % for me. Most of the time it appears to be rounding errors or perhaps time differentials.

 

[SolarBob]

Tesla app from Grid, 3377 kWh
to Grid, 3700 kWh

-323 kWh pretty close.

 

[charlesj]

Unless the PG&E meter is broken, they are right. They are revenue grade since they are charging you (or paying you) for the energy. Tesla is just using CTs which are not as accurate.

,,,

And @SolarBob

Since I have both Tesla App reporting and Enphase reporting directly from the micros on production at least with a CT from Tesla on my solar breaker,
The two are within 0.5% difference in production at end of day. Enphase claims their micros are revenue grade readers inside the micros.

So, the only answer might be for OP's issue is how he is running his system, standby or something else, and the the losses in transfers from and charging by the battery, even in backup only, there is a loss that doesn't get to the grid in overproduction.
Also, house usage is not from a direct reading of energy going strictly to the house but some sort of algorithm. There may be another reading inside the battery before/after losses may or may not be accounted for.
Lots of room where that simple calc by OP may have caused that difference; not a simple answer, I would think.

 

[seenhear]

And @SolarBob

Since I have both Tesla App reporting and Enphase reporting directly from the micros on production at least with a CT from Tesla on my solar breaker,
The two are within 0.5% difference in production at end of day. Enphase claims their micros are revenue grade readers inside the micros.

So, the only answer might be for OP's issue is how he is running his system, standby or something else, and the the losses in transfers from and charging by the battery, even in backup only, there is a loss that doesn't get to the grid in overproduction.
Also, house usage is not from a direct reading of energy going strictly to the house but some sort of algorithm. There may be another reading inside the battery before/after losses may or may not be accounted for.
Lots of room where that simple calc by OP may have caused that difference; not a simple answer, I would think.

Just curious, how did you get Enphase microinverters on a Tesla system?

 

[BGbreeder]

Just curious, how did you get Enphase microinverters on a Tesla system?

You buy from a third party, or you were lucky enough to add Powerwalls back when Tesla sold them separately...

 

[charlesj]

You buy from a third party, or you were lucky enough to add Powerwalls back when Tesla sold them separately...

Just curious, how did you get Enphase microinverters on a Tesla system?

I had Enphase for 10 years without batteries. I got tired of using a generator and messing with it with a 120V side on first floor to run refridge and freezer and candles and flashlight to shower by.
Then I discovered the Tesla batteries and after getting a very expensive quote from a local installer, Tesla direct was it. Easy to match them up as the solar is on the 2nd floor breaker panel with a 20A breaker.
Tesla slapped a current sensor up there and it works great for a couple of years now.
It seems they don't install just batteries now. Maybe when there is a better supply of them.